1. Field of the Invention
The present invention relates to, for example, in a recording apparatus such as a printer for outputting information retained in a computer or the like or in an image forming apparatus such as a copying machine and a facsimile, a recording apparatus which records image data on a recording medium through the use of a recording head, and a control method therefor.
2. Description of Related Art
A prior recording apparatus is equipped with a print head in which nozzles for formation of recording dots on a recording medium are made at a predetermined pitch and a conveying mechanism for conveying the recording medium, on which printing is effected by this print head, at a predetermined timing, so that recording dots are formed on the recording medium, thereby accomplishing the recording.
In general, a conveying mechanism comprises a conveying roller made of a rubber or the like and a motor for driving the conveying roller, and is designed to convey a recording medium by transferring a driving force of the motor through a transfer mechanism such as a gear up to the conveying roller. In addition, a type providing a minimum drive unit, such as a stepping motor, is used as the motor, and the specification including the gear ratio and the roller diameter is determined so that the conveying quantity of the recording medium assumes a predetermined value with respect to the minimum drive unit of the motor.
Furthermore, hitherto, in cases where the nozzle pitch of a print head coincides with the pitch of the recording dots to be formed on the recording medium, the conveying quantity of a recording medium relative to the minimum drive unit of a drive motor equals the pitch of recording dots to be formed on the recording medium or assumes integer times the pitch of recording dots, and in the case that the nozzle pitch of the print head assumes integer times the pitch of the recording dots to be formed on the recording medium, the conveying quantity becomes equal to the pitch of the recording dots to be formed on the recording medium.
FIG. 21 is an illustration of a print pattern taken when a nozzle pitch of a print head assumes integer times the pitch of recording dots to be formed on a recording medium.
In FIG. 21, a distance Pd represents a pitch of recording dots formed on a recording medium, a distance Ph designates an arrangement pitch of nozzles of a print head, and a distance L denotes a recording medium conveying quantity at step of a stepping motor, where Ph=4Pd.
Columns C0 to C3 signify nozzle positions of the print head in conveying the recording medium. In this instance, a conveying quantity L corresponding to one step of the stepping motor is set to be equal to the recording dot pitch Pd, and if the recording medium is conveyed by a quantity being integer times of L in a feeding direction S of the recording medium in FIG. 21, the print head relatively shifts with respect to the recording medium as indicated by the columns C1, C2 and C3, and therefore, the recording dots can be formed on the recording medium at a predetermined recording dot pitch Pd.
The conveying quantity of the recording medium is set to integer times the basic conveying quantity L for the formation of the recording dots at the respective recording positions to correspond to the number of nozzles installed in the print head.
 less than Problems to be Solved By the Invention greater than 
However, recently, it has been necessary to make the pitch of the recording dots smaller so that the quality of a recording image is higher, and the reduction of the pitch of the recording dots to be formed by a print head has quickly taken place.
For this reason, with the above-mentioned prior art construction, if the conveying quantity of a recording medium corresponding to the minimum drive unit of a stepping motor is set to be equal to the pitch of recording dots to be formed on the recording medium, the conveying quantity per one step of the stepping motor is reduced. However, since there is a limit to the number of steps to be allowed at the drive of the stepping motor within a constant time, the conveying speed of the recording medium becomes low, thereby causing the reduction of the throughput related to the performance of the recording apparatus.
In addition, for solving the aforesaid defect, there is a need to use a high-priced motor with a high drive performance, which increases the apparatus cost.
Moreover, in the case that the conveying quantity of a recording medium corresponding to the minimum drive unit of the stepping motor is set to integer times the pitch of recording dots to be formed on the recording medium, although the recording dot pitch is needed to be equal to the nozzle pitch of the print head, there is a limit to the reduction of the nozzle pitch of the print head, so that difficulty is experienced in reducing it to below a predetermined pitch, so that higher image quality recording becomes impossible.
Besides, since the reduction of the nozzle arrangement pitch of the print head involves the difficulty in processing, the cost of the print head rises, which has influence on the cost of the whole apparatus.
Accordingly, the present invention has been developed with view to eliminating the above-mentioned problems of the prior art, and it is an object of this invention to provide a low-cost recording apparatus which is capable of increasing a recording medium conveying speed and of accomplishing recording of a high quality at a small recording dot pitch, and further to provide a control method therefor.
For eliminating the above-mentioned problems and for achieving the purpose, a recording apparatus according to this invention is constructed as follows. That is, the recording apparatus comprises a recording head having a plurality of discharge ports for discharging inks, said plurality of discharge ports are arranged at a predetermined pitch, a scanning means for scanning the recording head in scanning (main scanning) directions, a conveying means for conveying a recording medium in a conveying (sub-scanning) direction, and a control means for controlling the conveying means at integer times the minimum conveying unit. The control means controls the conveying means so that ink is discharged onto a recording medium at a recording dot pitch obtained by dividing the predetermined pitch of the discharge ports by an integer above 2, and a conveying quantity of the recording medium corresponding to the minimum conveying unit of the conveying means becomes larger than the pitch of the recording dots to be formed on the recording medium.
For eliminating the above-mentioned problems and for achieving the purpose, a recording apparatus according to this invention is constructed as follows.
That is, according to this invention, a recording apparatus comprises a recording head having a plurality of discharge ports for discharging inks, said plurality of discharge ports are arranged at a predetermined pitch, a scanning means for scanning the recording head in scanning directions, a conveying means for conveying a recording medium in a conveying direction, and a control means for controlling the conveying means at integer times its minimum conveying unit. The recording head discharges ink onto a recording medium at a recording dot pitch obtained by dividing the predetermined pitch of the discharge ports by an integer above 2, while the control means controls the conveying means to, when the conveying quantity of the recording medium is taken to be L, the pitch of the discharge ports is taken as Ph and the recording dot pitch is taken as Pd, satisfy the condition of Ph/Pdxe2x89xa72 and L greater than Pd.
For eliminating the above-mentioned problems and for achieving the purpose, a control method for a recording apparatus according to this invention has the following features.
That is, according to this invention, in a control method for a recording apparatus comprising a recording head having a plurality of discharge ports for discharging inks, said plurality of discharge ports are arranged at a predetermined pitch, a scanning means for scanning the recording head in scanning directions, a conveying means for conveying a recording medium in a conveying direction, and a control means for controlling the conveying means at integer times its minimum conveying unit, the ink is discharged onto a recording medium at a recording dot pitch obtained by dividing the predetermined pitch of the discharge ports by an integer above 2, and the conveying means is controlled so that a feed quantity of the recording medium corresponding to the minimum conveying unit of the conveying means becomes larger than the pitch of the recording dots to be formed on the recording medium.
For eliminating the above-mentioned problems and for achieving the purpose, a control method for a recording apparatus according to this invention has the following features.
That is, according to this invention, in a control method for a recording apparatus comprising a recording head having a plurality of discharge ports for discharging inks, said plurality of discharge ports are arranged at a predetermined pitch, a scanning means for scanning the recording head in scanning directions, a conveying means for conveying a recording medium in a conveying direction, and a control means for controlling the conveying means at integer times its minimum conveying unit, the ink is discharged onto the recording medium at a recording dot pitch obtained by dividing the predetermined pitch of the discharge ports by an integer above 2, while the conveying means is controlled so that, when a conveying quantity of the recording medium is taken to be L, the pitch of the discharge ports is taken as Ph and the recording dot pitch is taken as Pd, the condition of Ph/Pdxe2x89xa72 and L greater than Pd is satisfied.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.